The development of high‐performance nonprecious metal catalysts(NPMCs)to supersede Pt‐based catalysts for the oxygen reduction reaction(ORR)in polymer electrolyte membrane fuel cells is highly desirable but remains ...The development of high‐performance nonprecious metal catalysts(NPMCs)to supersede Pt‐based catalysts for the oxygen reduction reaction(ORR)in polymer electrolyte membrane fuel cells is highly desirable but remains challenging.In this paper,we present a pyrolysis strategy for spatial confinement and active‐site fixation using iron phthalocyanine(FePc),phthalocyanine(Pc)and Zn salts as precursors.In the obtained carbon‐based NPMC with a hierarchically porous nanostructure of thin‐layered carbon nanosheets,nearly 100%of the total Fe species are Fe^(Ⅱ)‐N_(4) active sites.In contrast,pyrolyzing FePc alone forms Fe‐based nanoparticles embedded in amorphous carbon with only 5.9%Fe^(Ⅱ)‐N_(4) active sites.Both experimental characterization and density functional theory calculations reveal that spatial confinement through the staggeredπ–πstacking of Pc macrocycles effectively prevents the demetallation of Fe atoms and the formation of Fe‐based nanoparticles via aggregation.Furthermore,Zn‐induced microporous defects allow the fixation of Fe^(Ⅱ)‐N_(4) active sites.The synergistic effect of staggered stacking confinement and microporous defect fixation results in a high density of atomic Fe^(Ⅱ)‐N_(4) active sites that can enhance the ORR.The optimal Fe^(Ⅱ)‐N_(4)‐C electro‐catalyst outperforms a commercial Pt/C catalyst in terms of half‐wave potential,methanol toler‐ance,and long‐term stability in alkaline media.This modulation strategy can greatly advance efforts to develop high‐performance NPMCs.展开更多
Electrochemical energy systems such as fuel cells and metal–air batteries can be used as clean power sources in the field of electric transportation and possess great potential in the reduction of various energy and ...Electrochemical energy systems such as fuel cells and metal–air batteries can be used as clean power sources in the field of electric transportation and possess great potential in the reduction of various energy and environmental issues.In these systems,the oxygen reduction reaction(ORR)at the cathode is the rate-determining factor for overall system performance,and up to now,platinum group metals supported on carbon materials,especially Pt,remain the highest performing and the most practical ORR electrocatalysts.However,corresponding carbonaceous catalyst supports are extremely susceptible to corrosion under electrochemical operation,and therefore,the extensive exploration of alternative stable materials for ORR electrocatalysts with both high electrochemical stability and catalytic performance is essential.Here,noncarbon materials with high corrosion resistance have been explored to substitute traditional carbon supports or even act directly as low-cost non-noble metal electrocatalysts,and based on this,this review will present a comprehensive overview and deep analysis of the recent progress in noncarbon materials,including metals,oxides,nitrides,carbides,sulfides,and so on.Overall,general attributes associated with noncarbon materials include high corrosion resistance,strong metal–support interaction,and impressive porous structure retention.However,major drawbacks include low electrical conductivity,insufficient chemical stability in acidic or alkaline media,and poor electrochemical stability at ORR electrode potentials.To overcome these challenges,this review will also summarize efficient strategies such as combining with highly conductive materials,introducing dopants and forming vacancies to result in promising electrocatalytic ORR performances.Finally,this review will propose possible research directions to facilitate future research and development toward the practical application of noncarbon-based ORR electrocatalysts.展开更多
文摘The development of high‐performance nonprecious metal catalysts(NPMCs)to supersede Pt‐based catalysts for the oxygen reduction reaction(ORR)in polymer electrolyte membrane fuel cells is highly desirable but remains challenging.In this paper,we present a pyrolysis strategy for spatial confinement and active‐site fixation using iron phthalocyanine(FePc),phthalocyanine(Pc)and Zn salts as precursors.In the obtained carbon‐based NPMC with a hierarchically porous nanostructure of thin‐layered carbon nanosheets,nearly 100%of the total Fe species are Fe^(Ⅱ)‐N_(4) active sites.In contrast,pyrolyzing FePc alone forms Fe‐based nanoparticles embedded in amorphous carbon with only 5.9%Fe^(Ⅱ)‐N_(4) active sites.Both experimental characterization and density functional theory calculations reveal that spatial confinement through the staggeredπ–πstacking of Pc macrocycles effectively prevents the demetallation of Fe atoms and the formation of Fe‐based nanoparticles via aggregation.Furthermore,Zn‐induced microporous defects allow the fixation of Fe^(Ⅱ)‐N_(4) active sites.The synergistic effect of staggered stacking confinement and microporous defect fixation results in a high density of atomic Fe^(Ⅱ)‐N_(4) active sites that can enhance the ORR.The optimal Fe^(Ⅱ)‐N_(4)‐C electro‐catalyst outperforms a commercial Pt/C catalyst in terms of half‐wave potential,methanol toler‐ance,and long‐term stability in alkaline media.This modulation strategy can greatly advance efforts to develop high‐performance NPMCs.
基金the Natural Science Foundation of China(Grant Nos.21606149,21832004,U1905215,and 51672046)Shanghai Rising-Star Program(18QB1404400)National Key Research and Development Program/Key Scientific Issues of Transformative Technology(2020YFA0710303).
文摘Electrochemical energy systems such as fuel cells and metal–air batteries can be used as clean power sources in the field of electric transportation and possess great potential in the reduction of various energy and environmental issues.In these systems,the oxygen reduction reaction(ORR)at the cathode is the rate-determining factor for overall system performance,and up to now,platinum group metals supported on carbon materials,especially Pt,remain the highest performing and the most practical ORR electrocatalysts.However,corresponding carbonaceous catalyst supports are extremely susceptible to corrosion under electrochemical operation,and therefore,the extensive exploration of alternative stable materials for ORR electrocatalysts with both high electrochemical stability and catalytic performance is essential.Here,noncarbon materials with high corrosion resistance have been explored to substitute traditional carbon supports or even act directly as low-cost non-noble metal electrocatalysts,and based on this,this review will present a comprehensive overview and deep analysis of the recent progress in noncarbon materials,including metals,oxides,nitrides,carbides,sulfides,and so on.Overall,general attributes associated with noncarbon materials include high corrosion resistance,strong metal–support interaction,and impressive porous structure retention.However,major drawbacks include low electrical conductivity,insufficient chemical stability in acidic or alkaline media,and poor electrochemical stability at ORR electrode potentials.To overcome these challenges,this review will also summarize efficient strategies such as combining with highly conductive materials,introducing dopants and forming vacancies to result in promising electrocatalytic ORR performances.Finally,this review will propose possible research directions to facilitate future research and development toward the practical application of noncarbon-based ORR electrocatalysts.
